Heparin Monitoring (APTT)
APTT, APTT Ratio
Monitoring of unfractionated heparin therapy.
Note: for patients on low molecular weight
heparin see Anti-Xa assay
Request via ICE
Patient should be bled with minimal stasis
Patient should ideally be at rest
Fresh citrated Blood; sample must be received by the laboratory
within 4 hours of collection.
Blue capped vacutainer tube
Clean venepuncture. Samples must be received by the laboratory
within 4 hours of collection
Causes for Rejection
Underfilled, clotted, haemolysed or if sample is too old.
An APTT ratio of 1.5 - 3.0 equates to a therapeutic heparin dose
(0.2 to 0.5U heparin / mL plasma